Simard: I don’t think it will be blocked. We’re looking at how those grasslands, which are primarily arbuscular mycorrhizal, interact with our ectomycorrhizal forest, because as climate changes, the grasslands are predicted to move up into the forests.Į360: Will these exchanges continue under climate change, or will communication be blocked? In British Columbia, we have big grasslands that come up through the interior of the province and interface with the forest. Simard: Yes, not just in my lab, but also in other labs well before me”¦ Grasslands, and even some of the tree species we’re familiar with like maple and cedar, form a different type of mycorrhiza. I don’t think there’s ever going to be a shortage of an ability to form a network, but the network might be different.Į360: Do you think this exchange system holds true in other ecosystems as well, like grasslands, for instance? Has there been any work done on that? The fungus is in it for its own livelihood, to make sure that it’s got a secure food base in the future, so it will help direct that carbon transfer to the different plants. Even though we don’t understand a whole lot about that, it makes sense from an evolutionary point of view. For example, fungus that is linking the network is going to be looking to secure its carbon sources. There are also probably fungal factors involved. Then later in the fall, when the birch was losing its leaves and the fir had excess carbon because it was still photosynthesizing, the net transfer of this exchange went back to the birch. The more Douglas fir became shaded in the summertime, the more excess carbon the birch had went to the fir. One of the important things that we tested in that particular experiment was shading. It depends on the ecological factors that are going on at the time. Keep in mind that it’s a back and forth exchange, so sometimes the birch will get more and sometimes the fir will get more. We’ve done a bunch of experiments trying to figure out what drives the exchange. They compete with each other, but our work shows that they also cooperate with each other by sending nutrients and carbon back and forth through their mycorrhizal networks.Į360: And they can tell when one needs some extra help versus the other, is that correct? In a natural forest of British Columbia, paper birch and Douglas fir grow together in early successional forest communities. It’s this network, sort of like a below-ground pipeline, that connects one tree root system to another tree root system, so that nutrients and carbon and water can exchange between the trees. The plant is fixing carbon and then trading it for the nutrients that it needs for its metabolism. Basically, it sends mycelium, or threads, all through the soil, picks up nutrients and water, especially phosphorous and nitrogen, brings it back to the plant, and exchanges those nutrients and water for photosynthate from the plant. These are fungi that are beneficial to the plants and through this association, the fungus, which can’t photosynthesize of course, explores the soil. Suzanne Simard: All trees all over the world, including paper birch and Douglas fir, form a symbiotic association with below-ground fungi. You used radioactive isotopes of carbon to determine that paper birch and Douglas fir trees were using an underground network to interact with each other. Yale Environment 360: Not all PhD theses are published in the journal Nature. “Whether they’re beneficial to native plant species, or exotics, or invader weeds and so on, that remains to be seen.” Simard is now focused on understanding how these vital communication networks could be disrupted by environmental threats, such as climate change, pine beetle infestations, and logging. If we care about it more, then we’re going to do a better job of stewarding our landscapes.” If we can relate to it, then we’re going to care about it more. We as human beings can relate to this better. “To me, using the language of ‘communication’ made more sense because we were looking at not just resource transfers, but things like defense signaling and kin recognition signaling. “A forest is a cooperative system,” she said in an interview with Yale Environment 360. By using phrases like “forest wisdom” and “mother trees” when she speaks about this elaborate system, which she compares to neural networks in human brains, Simard’s work has helped change how scientists define interactions between plants.
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